Implement blackbox in Golang (#250)

* Initial release

pkg/commitlater/commitlater.go

@@ -0,0 +1,84 @@
+package commitlater
+
+import (
+	"fmt"
+)
+
+type future struct {
+	message string   // Message that describes this transaction.
+	dir     string   // Basedir of the files
+	files   []string // Names of the files
+	display []string // Names as to be displayed to the user
+}
+
+// List of futures to be done in the future.
+type List struct {
+	items []*future
+}
+
+// Add queues up a future commit.
+func (list *List) Add(message string, repobasedir string, files []string) {
+	item := &future{
+		message: message,
+		dir:     repobasedir,
+		files:   files,
+	}
+	list.items = append(list.items, item)
+}
+
+func sameDirs(l *List) bool {
+	if len(l.items) <= 1 {
+		return true
+	}
+	for _, k := range l.items[1:] {
+		if k.dir != l.items[0].dir {
+			return false
+		}
+	}
+	return true
+}
+
+// Flush executes queued commits.
+func (list *List) Flush(
+	title string,
+	fadd func([]string) error,
+	fcommit func([]string, string, []string) error,
+) error {
+
+	// Just list the individual commit commands.
+	if title == "" || len(list.items) < 2 || !sameDirs(list) {
+		for _, fut := range list.items {
+			err := fadd(fut.files)
+			if err != nil {
+				return fmt.Errorf("add files1 (%q) failed: %w", fut.files, err)
+			}
+			err = fcommit([]string{fut.message}, fut.dir, fut.files)
+			if err != nil {
+				return fmt.Errorf("commit files (%q) failed: %w", fut.files, err)
+			}
+		}
+		return nil
+	}
+
+	// Create a long commit message.
+	var m []string
+	var f []string
+	for _, fut := range list.items {
+		err := fadd(fut.files)
+		if err != nil {
+			return fmt.Errorf("add files2 (%q) failed: %w", fut.files, err)
+		}
+		m = append(m, fut.message)
+		f = append(f, fut.files...)
+	}
+	msg := []string{title}
+	for _, mm := range m {
+		msg = append(msg, "    * "+mm)
+	}
+	err := fcommit(msg, list.items[0].dir, f)
+	if err != nil {
+		return fmt.Errorf("commit files (%q) failed: %w", f, err)
+	}
+
+	return nil
+}